1. Field of the Invention
The invention of the present patent application relates to a process for the production of an aromatic polycarbonate resin required to have high quality such as a resin for optical use. The required high quality includes thermal stability, transparency, foreign matter content, etc., as well as color.
More particularly, the present invention relates to a process for the production of an aromatic polycarbonate resin mainly by melt polycondensation method and to a process capable of producing an aromatic polycarbonate resin having excellent color and transparency in high efficiency while keeping the color stability, thermal stability, etc., of the aromatic polycarbonate resin during the production process.
Further, the present invention relates to a process for the production of an aromatic polycarbonate resin having low foreign matter content, especially to a process for the production of an aromatic polycarbonate resin having low foreign matter content by using a polymer filter.
The collective improvement in the quality level of an aromatic polycarbonate resin on the color, thermal stability, transparency, foreign matter content, etc., is keenly demanded in the highly developed recent fields such as optical applications.
2. Description of the Related Art
Aromatic polycarbonate resin is widely known in general as an extremely useful resin owing to its excellent characteristics such as impact resistance and transparency. Aromatic polycarbonate resin can be produced by an interfacial method comprising the reaction of an aromatic dihydroxy compound (in the present-specification, xe2x80x9caromatic dihydroxy compoundxe2x80x9d is sometimes called as xe2x80x9caromatic diol compoundxe2x80x9d) with phosgene in a mixture of an organic solvent and an alkaline aqueous solution and a melt polycondensation method comprising the reaction of an aromatic dihydroxy compound with a carbonic acid diester in the presence of a catalyst at high temperature and reduced pressure to remove the generated phenol from the system.
The foreign matters in an aromatic polycarbonate resin are classified generally into foreign materials contaminated through the raw materials or from outside the reaction system and foreign materials generated in the reactor or a flow path of a high-viscosity material after the reaction. Intrusion of the former foreign matters is prevented by providing a filter for the filtration of foreign matter in raw materials or improving the sealing of the reaction system, and the latter foreign matters are removed by filtering with a filter immediately before processing the high-viscosity material into a desired form.
The development of the melt polycondensation method is being pushed forward because of the limited environmental problem and the possibility to be advantageous from the viewpoint of cost since the method does not use harmful phosgene and methylene chloride as a solvent, however, the quality of the produced aromatic polycarbonate has the problem of inferior color and gel content compared with the polymer produced by interfacial polymerization method.
In the melt polycondensation method, the reaction mixture is transferred between reactors or discharged from the reactor in a hot molten state and the molten reaction mixture is exposed to high temperature during the transfer between reactors or the discharge from the reactor occasionally to cause the discoloration of the polymer or the generation of foreign matters and deteriorate the excellent characteristics such as transparency of the aromatic polycarbonate resin. The discoloration and the generation of foreign matter are undesirable from the viewpoint of product quality especially in an aromatic polycarbonate resin used in an optical use such as compact disk.
Various proposals were presented mainly on the polymerization facility and catalyst, etc., to settle the problems, however, the effects of these measures were still insufficient and there are restrictions in the case of using the resin to an optical use or a sheet such as compact disk required to have high quality.
Furthermore, deterioration caused by retention of the resin such as discoloration, crosslinking and gel-formation is liable to take place in a filter depending upon the temperature and viscosity of the liquid to be filtered, and the size of a particle retained and the amount treated by the filter, exerting considerable influence on the product quality.
These problems are serious especially in an aromatic polycarbonate resin recently applied to optical uses such as DVD, MO and CDR which are required to have high recording density and high precision because the problems of foreign matter, discoloration and gel have direct influence on the optical characteristics such as block error rate and the mechanical characteristics such as tensile properties, flexural properties and toughness of the final product. Further, as the gel particles have a characteristic of changing its shape, gel particles larger than the retained particle size of the filter can pass through the filter to cause an extremely serious problem owing to the deformability of gel particle.
The object of the present invention is to improve the above problems of the conventional technique and provide a process for producing an aromatic polycarbonate resin having excellent quality.
The process of the present invention can produce an aromatic polycarbonate resin having excellent color and free from foreign matter without deterioration of quality in a pipe during the production process because of the high flow speed of the molten reaction mixture in the pipe to decrease the thermal history in the pipe and the smooth flow of the reaction mixture in the pipe, produce, in high efficiency, an aromatic polycarbonate resin having excellent color and transparency as well as excellent color stability and thermal stability by the proper use of a catalyst deactivation agent, and relieve the above problems of conventional technique by the use of the filtration method by the present invention in which an aromatic polycarbonate resin and molded article having excellent quality is obtained by efficiently removing the foreign matters with a polymer filter, while, at the same time, suppressing the discoloration, crosslinking and generation of gel in the filter.
In the specification of the present application, the term xe2x80x9creaction mixturexe2x80x9d means a mixture at the starting or proceeding reaction stage of polycondensation reaction in a process for producing an aromatic polycarbonate resin by the melt polycondensation reaction of a mixture containing an aromatic dihydroxy compound and an aromatic carbonic acid diester as main components in the presence of a transesterification catalyst, etc., comprising a nitrogen-containing basic compound and an alkali metal compound and/or alkaline earth metal compound. A mixture having polymerization degree increased to a certain extent is called as a xe2x80x9cprepolymerxe2x80x9d by the general chemical term. A mixture having further increased polymerization degree is called a xe2x80x9cpolymerxe2x80x9d by the general chemical term.
The invention of the present application comprises the following items.
1. A process for the production of an aromatic polycarbonate resin comprising filtering an aromatic polycarbonate resin having a viscosity-average molecular weight of 10,000 or more in a molten state with a filter having a retained particle size of 40 xcexcm or less under a pressure difference of 20 kg/cm2 or more.
2. The process for the production of an aromatic polycarbonate resin according to item 1, wherein the filter having a retained particle size of 40 xcexcm or less is a filter having a retained particle size of 20 xcexcm or less.
3. A process for the production of an aromatic polycarbonate resin comprising filtering an aromatic polycarbonate resin having a viscosity-average molecular weight of 10,000 or more in a molten state with a filter having a retained particle size of 10 xcexcm or less under a pressure difference of 40 kg/cm2 or more.
4. The process for the production of an aromatic polycarbonate resin according to any one of items 1 to 3, wherein a quantity of the aromatic polycarbonate resin to be treated is 50 kg/m2/hr or more based on a unit area of the filter.
5. The process for the production of an aromatic polycarbonate resin according to any one of the above items 1 to 3, wherein a ratio V/W of volume V (L) in a filtration vessel to flow rate W (L/min) of the filtered polymer is within a range of 0.2 to 10 min.
6. The process for the production of an aromatic polycarbonate resin according to any one of items 1 to 3, wherein a maximum area A (cm2) of a polymer flow path in a filtration vessel and a flow rate W satisfy the requirement that a value Wxc3x971,000/A is from 1 cm/min to 10,000 cm/min.
7. The process for the production according to any one of items 1 to 3, wherein the aromatic polycarbonate resin is an aromatic polycarbonate resin produced by polycondensation of an aromatic diol compound and a carbonic acid diester compound in the presence or absence of a catalyst.
8. The process for production according to any one of items 1 to 3, wherein the aromatic polycarbonate resin produced by the polycondensation of an aromatic diol compound and a carbonic acid diester compound in the presence or absence of a catalyst is, after the addition of an additive as required, directly filtered with a filter in molten state without cooling and solidifying the resin.
9. A process for the production of an aromatic polycarbonate resin comprising adding a catalyst deactivation agent to a system within 2 hours after completion of a melt polycondensation reaction in the production of an aromatic polycarbonate resin by the melt polycondensation of a mixture containing an aromatic dihydroxy compound and an aromatic carbonic acid diester as main components in the presence of a catalyst.
10. A process for the production of an aromatic polycarbonate resin wherein a flow velocity of a reaction mixture in a pipe through which a molten reaction mixture passes is 0.5 cm/sec or more in a production of an aromatic polycarbonate resin by continuous melt polycondensation of a mixture containing an aromatic dihydroxy compound and an aromatic carbonic acid diester as main components in the presence of a catalyst.
11. A process for the production of an aromatic polycarbonate resin wherein a flow velocity of a reaction mixture in a pipe through which a molten reaction mixture passes is 2 cm/sec or more in a production of an aromatic polycarbonate resin by continuous melt polycondensation of a mixture containing an aromatic dihydroxy compound and an aromatic carbonic acid diester as main components in the presence of a catalyst.
12. The process for the production of an aromatic polycarbonate resin according to the item 10 or 11, wherein a viscosity-average molecular weight of the reaction mixture in a pipe through which the molten reaction mixture passes is 1,000 or more.
13. The process for the production of an aromatic polycarbonate resin according to the item 10 or 11, wherein a viscosity-average molecular weight of the reaction mixture in a pipe through which the molten reaction mixture passes is 10,000 or more.
14. The process for the production of an aromatic polycarbonate resin according to the item 10 or 11, wherein a sum of average retention times of the reaction mixture in pipes through which the molten reaction mixture passes is not longer than 3 hours.
15. The process for the production of an aromatic polycarbonate resin according to the item 10 or 11, wherein a wall surface temperature of a pipe through which the molten reaction mixture passes is set to be higher than a temperature of the reaction mixture in the pipe.
16. The process for the production of an aromatic polycarbonate resin according to the item 10 or 11, wherein the pipe through which the molten reaction mixture passes is a cold-drawn stainless steel pipe.
17. The process for the production of an aromatic polycarbonate resin according to the item 10 or 11, wherein the pipe through which the molten reaction mixture passes is a stainless steel pipe having-a buff-finished inner surface.
18. The process for the production of an aromatic polycarbonate resin according to item 8, wherein a catalyst deactivation agent is added to a system within 2 hours after completion of the melt polycondensation reaction in the production of an aromatic polycarbonate resin by the melt polycondensation of mixture containing an aromatic dihydroxy compound and an aromatic carbonic acid diester as main components in the presence of a catalyst.
19. The process for the production of an aromatic polycarbonate resin according to item 8, wherein the flow velocity of a reaction mixture in a pipe through which the molten reaction mixture passes is 0.5 cm/sec or more in the production of an aromatic polycarbonate resin by the continuous melt polycondensation of a mixture containing an aromatic dihydroxy compound and an aromatic carbonic acid diester as main components in the presence of a catalyst.
20. The process for the production of an aromatic polycarbonate resin described in item 18, wherein the flow velocity of a reaction mixture in a pipe through which the molten reaction mixture passes is 0.5 cm/sec or more in the production of an aromatic polycarbonate resin by the continuous melt polycondensation of a mixture containing an aromatic dihydroxy compound and an aromatic carbonic acid diester as main components in the presence of a catalyst.
21. A molded article of an aromatic polycarbonate resin produced by directly processing an aromatic polycarbonate resin obtained by the method of item 8 into a desired product form without cooling and solidifying the produced resin.
22. A molded article of an aromatic polycarbonate resin produced by directly processing an aromatic polycarbonate resin obtained by the method according to item 18 into a desired product form without cooling and solidifying the produced resin.
23. A molded article of an aromatic polycarbonate resin produced by directly processing an aromatic polycarbonate resin obtained by the method according to item 19 into a desired product form without cooling and solidifying the produced resin.
24. A molded article of an aromatic polycarbonate resin produced by directly processing an aromatic polycarbonate resin obtained by a method according to item 20 into a desired product form without cooling and solidifying the produced resin.
25. The process for the production of an aromatic polycarbonate resin according to item 8, wherein the viscosity-average molecular weight of the reaction mixture in a pipe through which the molten reaction mixture passes is 10,000 or more.
26. The process for the production of an aromatic polycarbonate resin according to item 8, wherein a wall surface temperature of a pipe through which the molten reaction mixture passes is set to be higher than the temperature of the reaction mixture in the pipe.
27. The process for the production of an aromatic polycarbonate resin described in item 18, wherein the viscosity-average molecular weight of the reaction mixture in a pipe through which the molten reaction mixture passes is 10,000 or more.
28. The process for the production of an aromatic polycarbonate resin according to item 18, wherein a wall surface temperature of a pipe through which the molten reaction mixture passes is set to be higher than the temperature of the reaction mixture in the pipe
29. A molded article of an aromatic polycarbonate resin produced by directly processing an aromatic polycarbonate resin obtained by the method according to item 25 into a desired product form without cooling and solidifying the produced resin.
30. A molded article of an aromatic polycarbonate resin produced by directly processing an aromatic polycarbonate resin obtained by the method according to item 26 into a desired product form without cooling and solidifying the produced resin.
31. A molded article of an aromatic polycarbonate resin produced by directly processing an aromatic polycarbonate resin obtained by the method according to item 27 into a desired product form without cooling and solidifying the produced resin.
32. A molded article of an aromatic polycarbonate resin produced by directly processing an aromatic polycarbonate resin obtained by the method according to item 28 into a desired product form without cooling and solidifying the produced resin
33. A process for the production of an aromatic polycarbonate resin comprising filtering an aromatic polycarbonate resin having a viscosity average molecular weight of 10,000 or more in a molten state with (1) a filter unit constructed by piling up a plurality of disk type filter elements having an outer diameter of 4 to 15 inches, an inner diameter/outer diameter ratio of 1/7 or more and a retained particle size of 40 xcexcm or less under (2) a pressure difference of 20 kg/cm2 or more.
34. The process for the production of an aromatic polycarbonate resin according to item 33, wherein the disk type filter elements have a retained particle size of 20 xcexcm or less.
35. The process for the production of an aromatic polycarbonate resin according to item 33, wherein the disk type filter elements have a retained particle size of 10 xcexcm or less and the pressure difference is 40 kg/cm2 or more.
36. The process for the production of an aromatic polycarbonate resin according to item 33, wherein the quantity of the aromatic polycarbonate resin to be treated is 50 kg/m2/hr or more based on the unit area of the filter unit.
37. The process for the production of an aromatic polycarbonate resin according to item 33, wherein the disk type filter elements have an inner diameter/outer diameter ratio of 1/5 or more.
38. The process for the production of an aromatic polycarbonate resin according to item 33, wherein the disk type filter elements have an outer diameter of 6 to 12 inches.
39. The process for the production of an aromatic polycarbonate resin according to item 33, wherein the filter unit is constructed by piling up together 5 to 500 disk type filter elements.
40. The process for the production of an aromatic polycarbonate resin according to item 33, wherein the distance between adjacent disk type filter elements of the filter unit is 5 mm or less.
41. The process for the production of an aromatic polycarbonate resin according to item 33, wherein one filter unit is installed in one filtration vessel.
42. The process for the production of an aromatic polycarbonate resin according to item 41, wherein the ratio (V/W) of the volume V (L) of the filtration vessel to the flow rate W (L/min) of the resin in the vessel is in the range of 0.2 to 10 min.
The process of the present invention for the production of an aromatic polycarbonate resin is concretely described as follows.
Aromatic dihydroxy compounds used in the present invention include, for example,
bis(4-hydroxyphenyl)methane,
2,2-bis(4-hydroxyphenyl)propane,
2,2-bis(4-hydroxy-3-methylphenyl)propane,
4,4-bis(4-hydroxyphenyl)heptane,
2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane,
2,2-bis(4-hydroxy-3,5-dibromophenyl)propane,
bis(4-hydroxyphenyl)oxide,
bis(3,5-dichloro-4-hydroxyphenyl)oxide,
p,pxe2x80x2-dihydroxydiphenyl,
3,3xe2x80x2-dichloro-4,4xe2x80x2-dihydroxydiphenyl,
bis(hydroxyphenyl)sulfone, resorcinol, hydroquinone,
1,4-dihydroxy-2,5-dichlorobenzene,
1,4-dihydroxy-3-methylbenzene,
bis(4-hydroxyphenyl)sulfide and
bis(4-hydroxyphenyl)sulfoxide, and an especially preferable compound is 2,2-bis(4-hydroxyphenyl)propane.
Carbonic acid diesters used in the present invention include, for example, diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis(diphenyl) carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate and dicyclohexyl carbonate, and diphenyl carbonate is especially preferable among the above examples.
The ratio of two kinds of raw materials to be used in the present invention described by the molar ratio obtained through dividing the used mol number of the carbonic acid diester by the used mol number of the aromatic dihydroxy compound, is preferably selected within the range of 1.00 to 1.10.
The aromatic polycarbonate resin of the present invention may further contain, as required, aliphatic diols such as ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and 1,10-decanediol, dicarboxylic acids such as succinic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, cyclohexanecarboxylic acid and terephthalic acid and oxy acids such as lactic acid, p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.
Although there is no particular restriction to the kind of catalyst to be used in the present invention, a transesterification catalyst comprising a basic nitrogen compound and an alkali metal compound and/or alkaline earth metal compound can be used in the process.
There is no particular restriction also on the alkali metal and/or alkaline earth metal compound to be used in the present invention as long as the compound does not cause deterioration of the color of the aromatic polycarbonate resin, and various known compounds can be used in the process.
Examples of alkali metal compound usable as a catalyst include hydroxide, bicarbonate, carbonate, acetate, nitrate, nitrite, sulfite, cyanate, thiocyanate, stearate, borohydride, benzoate, hydrogen phosphate, bisphenol salt and phenol salt of an alkali metal.
Concrete examples of the above compounds include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium bicarbonate, potassium bicarbonate, lithium bicarbonate, sodium carbonate, potassium carbonate, lithium carbonate, sodium acetate, potassium acetate, lithium acetate, sodium nitrate, potassium nitrate, lithium nitrate, sodium nitrite, potassium nitrite, lithium nitrite, sodium sulfite, potassium sulfite, lithium sulfite, sodium cyanate, potassium cyanate, lithium cyanate, sodium thiocyanate, potassium thiocyanate, lithium thiocyanate, sodium stearate, potassium stearate, lithium stearate, sodium borohydride, potassium borohydride, lithium borohydride, sodium phenylborate, sodium benzoate, potassium benzoate, lithium benzoate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, dilithium hydrogen phosphate, disodium salt, dipotassium salt or dilithium salt of bisphenol A, and sodium salt, potassium salt and lithium salt of phenol.
The alkaline earth metal compounds to be used as a catalyst include e.g. hydroxide, bicarbonate, carbonate, acetate, nitrate, nitrite, sulfite, cyanate, thiocyanate, stearate, benzoate, bisphenol salt and phenol salt of an alkaline earth metal
Concrete examples of the above compounds include calcium hydroxide, barium hydroxide, strontium hydroxide, calcium bicarbonate, barium bicarbonate, strontium bicarbonate, calcium carbonate, barium carbonate, strontium carbonate, calcium acetate, barium acetate, strontium acetate, calcium nitrate, barium nitrate, strontium nitrate, calcium nitrite, barium nitrite, strontium nitrite, calcium sulfite, barium sulfite, strontium sulfite, calcium cyanate, barium cyanate, strontium cyanate, calcium thiocyanate, barium thiocyanate, strontium thiocyanate, calcium stearate, barium stearate, strontium stearate, calcium borohydride, barium borohydride, strontium borohydride, calcium benzoate, barium benzoate, strontium benzoate, calcium salt, barium salt and strontium salt of bisphenol A and calcium salt, barium salt and strontium salt of phenol.
In the present invention, as is required, (a) an alkali metal salt of an ate complex of a group 14 element of the periodic table or (b) an alkali metal salt of an oxo acid of a group 14 element of the periodic table can be used as the alkali metal compound for the catalyst. The group 14 element of the periodic table means silicon, germanium or tin.
The alkali metal salts of ate complex of the group 14 element of the periodic table are compounds described in JP-A 7-268091 (hereunder, JP-A means xe2x80x9cJapanese Unexamined Patent Publicationxe2x80x9d), concretely, germanium (Ge) compounds such as NaGe(OMe)5, NaGe(OEt)3, NaGe(OPr)5, NaGe(OBu)5, NaGe(OPh)5, LiGe(OMe)5, LiGe(OBu)5 and LiGe(OPh)5.
Concrete examples of tin (Sn) compounds include NaSn(OMe)3, NaSn(OMe)2(OEt), NaSn(OPr)3, NaSn(O-n-C6H13)3, NaSn(OMe)5, NaSn(OEt)5, NaSn(OBu)5, NaSn(O-n-C12H25)5, NaSn(OEt), NaSn(OPh)5 and NaSnBu2(OMe)3.
Preferable examples of the alkali metal salt of oxo acid of the group 14 element of the periodic table include for example an alkali metal salt of silicic acid, an alkali metal salt of stannic acid, an alkali metal salt of germanium(II) acid (germanous acid) and an alkali metal salt of germanium(IV) acid (germanic acid).
The alkali metal salt of silicic acid is e.g. an acidic or neutral alkali metal salt of monosilicic acid or its condensation product, such as monosodium orthosilicate, disodium orthosilicate, trisodium orthosilicate and tetrasodium orthosilicate.
The alkali metal salt of stannic acid is e.g. an acidic or neutral alkali metal salt of monostannic acid or its condensation product, such as disodium monostannate (Na2SnO3.xH2O, x=0 to 5) and tetrasodium monostannate (Na4SnO4).
The alkali metal salt of germanium(II) acid (germanous acid) is e.g. an acidic or neutral alkali metal salt of monogermanous acid or its condensation product, such as monosodium germanite (NaHGeO2).
The alkali metal salt of germanium(IV) acid (germanic acid) is e.g. an acidic or neutral alkali metal salt of monogermanium(IV) acid or its condensation product, such as monolithium orthogermanate (LiH3GeO4), disodium orthogermanate, tetrasodium orthogermanate, disodium digermanate (Na2Ge2O5), disodium tetragermanate (Na2Ge4O9) and disodium pentagermanate (Na2Ge5O11).
The alkali metal compound or the alkaline earth metal compound are used as a catalyst preferably in an amount to give from 1xc3x9710xe2x88x928 to 5xc3x9710xe2x88x925 equivalent in terms of the alkali metal element or the alkaline earth metal element per 1 mol of the aromatic diol compound. More preferable ratio is 5xc3x9710xe2x88x927 to 1xc3x9710xe2x88x925 equivalent on the same basis. When the amount of the alkali metal element or alkaline earth metal element in the catalyst is out of the range of 1xc3x9710xe2x88x928 to 5xc3x9710xe2x88x925 equivalent, various undesirable problems arise such as bad influence on various properties of the produced aromatic polycarbonate resin and insufficient progress of transesterification reaction resulting in failure in getting an aromatic polycarbonate having high molecular weight.
The nitrogen-containing basic compounds to be used as a catalyst include, for example, ammonium hydroxides having alkyl group, aryl group, alkylaryl group, etc., such as tetramethylammonium hydroxide (Me4NOH), tetraethylammonium hydroxide (Et4NOH), tetrabutylammonium hydroxide (Bu4NOH), benzyltrimethylammonium hydroxide (xcfx86-CH2(Me)3NOH) and hexadecyltrimethylammonium hydroxide, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine and hexadecyldimethylamine and basic salts such as tetramethylammonium borohydride (Me4NBH4), tetrabutylammonium borohydride (Bu4NBH4), tetrabutylammonium tetraphenylborate (Me4NBPh4) and tetrabutylammonium tetraphenylborate (Bu4NBPh4).
The above nitrogen-containing basic compound is used preferably in an amount to give 1xc3x9710xe2x88x925 to 5xc3x9710xe2x88x923 equivalent in terms of the ammoniacal nitrogen atom in the nitrogen-containing basic compound based on 1 mol of the aromatic diol compound. The ratio is more preferably 2xc3x9710xe2x88x925 to 5xc3x9710xe2x88x924 equivalent, and especially preferably 5xc3x9710xe2x88x925 to 5xc3x9710xe2x88x924 equivalent on the same basis.
The ratio of the alkali metal compound, alkaline earth metal compound and nitrogen-containing basic compound to the charged aromatic diol compound (also called aromatic dihydroxy compound) is expressed in the present invention by xe2x80x9cW (numerical value) equivalent of Z (name of the compound) in terms of metal or basic nitrogen based on 1 mol of the aromatic dihydroxy compoundxe2x80x9d. It means that the amount of Z corresponds to W mol when Z has one sodium atom as in the case of sodium phenoxide or 2,2 -bis (4 -hydroxyphenyl) propane monosodium salt or has one basic nitrogen atom as in the case of triethylamine, and corresponds to W/2 mol when the compound has two sodium atoms, etc., as in the case of 2,2-bis(4-hydroxyphenylpropane)disodium salt.
At least one kind of cocatalyst selected from the group of oxo acids of the group 14 element of the periodic table and oxides of said element may be used as required in combination with the above catalyst in the polycondensation reaction of the present invention.
Undesirable side reactions such as branching reaction liable to occur during polycondensation reaction and the generation of foreign matter or burn mark in a molding apparatus during molding are more effectively suppressed without ill-affecting the terminal blocking reaction and polycondensation reaction rate by using these cocatalysts at specific ratios.
The present invention relating to the flow velocity of the reaction mixture is characterized by decreasing the thermal history applied to the reaction mixture in a pipe through which the mixture passes while being transferred between the reactors or discharged from the reactors in molten state and smoothing the flow of the reaction mixture in the pipe in the production of an aromatic polycarbonate resin by the continuous melt polycondensation of a mixture containing an aromatic dihydroxy compound and a carbonic acid diester as main components in the presence of a catalyst.
An aromatic polycarbonate resin having excellent color and free from foreign matter can be produced according to the production process of the aromatic polycarbonate resin of the present invention relating to the flow velocity of the reaction mixture without causing the deterioration of quality in a pipe in production, because the reaction mixture has high flow velocity in the pipe through which the molten reaction mixture passes, the mixture is subjected to little thermal history in the pipe and the reaction mixture flows smoothly in the pipe.
Melt-polymerization is attracting attention because it is a process for the production of an aromatic polycarbonate resin without using phosgene and halogenated solvents, causing little environmental problem and is expected to be advantageous from the viewpoint of cost, however, the process has a problem of giving a polymer inferior to an aromatic polycarbonate resin produced by interfacial polymerization in the quality, especially color and gel formation. Various methods were proposed to solve the problem, however, satisfiable method has not been found at present.
In consideration of the present status described above, the inventors of the present invention have studied the equipment to be used in the process while paying attention to the contact of the reaction mixture with the equipment and found that pipes accounting for major part in the contact area per unit volume exert considerable influence on the quality of the produced aromatic polycarbonate resin and attained the present invention.
According to the investigation performed by the inventors of the present invention, proposals paying attention to pipes are not absolutely absent heretofore, and a proposal specifying the surface roughness of a pipe to 5 xcexcm or less has been known. However, the proposal is insufficient by itself and it has been found that comprehensive consideration of several factors is necessary for attaining a considerable effect. Although the reason is not yet clear, the polymer quality is supposed to be remarkably influenced by two factors; the first supposed factor being that the reaction mixture is transferred in a pipe in the state of laminar flow owing to the generally high melt-viscosity of the reaction mixture and the laminar film (or boundary film) (a part contacting with the inner wall of the pipe and having extremely slow flow speed of the reaction mixture) in this state forms a pseudo-dead space; and the second supposed factor being that, in contrast with other condensation polymerization polymer such as polyethylene terephthalate, an aromatic polycarbonate resin has a characteristic of causing branching by itself to form a crosslinked structure to be gelled by the heating over a long period even if other factors such as oxygen are completely eliminated. The present invention comprises the elimination of the pseudo-dead space as completely as possible.
In the present invention relating to the flow velocity of the reaction mixture and producing an aromatic polycarbonate resin, the deterioration of the quality of the reaction mixture in a pipe can be decreased the more, the more the flow velocity of the molten reaction mixture passing through the pipe is increased, thus providing an aromatic polycarbonate resin having excellent color and free from foreign matter. The flow velocity of the molten reaction mixture in a pipe is preferably 0.5 cm/sec or more and especially preferably 2 cm/sec or more. The term xe2x80x9cpipexe2x80x9d which can also be referred to as xe2x80x9clinexe2x80x9d means a pipe connecting reactors through which the molten reaction mixture passes and a pipe through which the molten reaction mixture is discharged from the reactor.
In the present invention relating to the flow velocity of the reaction mixture, the viscosity-average molecular weight of the reaction mixture is preferably 1,000 or more, more preferably 10,000 or more in the process for the production of an aromatic polycarbonate resin. If the viscosity-average molecular weight is smaller than the above limit, the effect is decreased supposedly by the decrease of the generation of the pseudo-dead space.
It is important to shorten the average retention time of a reaction mixture in a pipe to decrease the thermal history of the reaction mixture in the pipe. In the process of the present invention relating to the flow velocity of the reaction mixture and producing an aromatic polycarbonate resin, the average retention time of the reaction mixture in a pipe is preferably 3 hours or shorter, more preferably 1 hour or shorter.
In the present invention relating to the flow velocity of the reaction mixture and producing an aromatic polycarbonate resin, it is preferable to set the wall surface temperature of the pipe through which the reaction mixture passes to be higher than the temperature of the reaction mixture passing through the pipe to decrease the melt viscosity of the reaction mixture on the wall surface of the pipe in order to make the flow of the reaction mixture smooth in the pipe and decrease the lowering of the flow velocity of the reaction mixture on the wall surface of the pipe. The wall temperature of the pipe is set to be higher than the temperature of the reaction mixture in the pipe by preferably 2 to 50xc2x0 C., more preferably 5 to 20xc2x0 C.
Processing method and material of the pipe are also important to attain smooth flow of the reaction mixture in a pipe connecting reactors or a pipe to discharge the mixture from a reactor. In the process of the present invention relating to the flow velocity of the reaction mixture and producing an aromatic polycarbonate resin, the pipe through which the molten reaction mixture passes is preferably a cold-drawn stainless steel pipe. The material of the stainless steel includes e.g. SUS304, SUS316 and SUS316L as specified by JIS.
In the process of the present invention relating to the flow, velocity of the reaction mixture and producing an aromatic polycarbonate resin, the inner surface of the pipe through which the molten reaction mixture passes is preferably subjected to buff-finish to make the flow of the reaction mixture smooth by forming as smooth a surface as possible. The degree of the buff-finishing treatment is preferably #100 or finer, more preferably #400 or finer.
It has been clarified that the quick deactivation of used polymerization catalyst after the polymerization of the above-mentioned raw materials with a catalyst is also extremely important in the present invention for getting an aromatic polycarbonate resin having excellent quality.
As a result of investigation performed by the inventors of the present invention, it has been found that an aromatic polycarbonate resin having excellent color and transparency can be produced, in the production of an aromatic polycarbonate resin by the melt-polycondensation of a mixture containing a carbonic acid diester and an aromatic dihydroxy compound in the presence of a catalyst, by shortening the retention time, in a molten state at a high temperature after the melt-polymerization reaction, of the aromatic polycarbonate resin containing the catalyst with remaining catalytic activity.
The cause is not yet clear, however, it is supposed as follows.
An aromatic polycarbonate resin with remaining catalytic activity is transferred in the apparatus in an non-evacuated molten state during the period after the completion of the polymerization reaction and before the discharge from the polymerization facility. Depolymerization reaction of the aromatic polycarbonate resin takes place during the retention time in the non-evacuated molten state at a high temperature by the phenol remaining in the aromatic polycarbonate resin as a reaction by-product and the catalyst with remaining catalytic activity. The depolymerization reaction decreases the molecular weight of the aromatic polycarbonate resin and increases the OH groups of the polymer terminals. The color of the polymer is supposed to be deteriorated during the retention time of the polymer with remaining catalytic activity in the non-evacuated hot molten state because the increase of the OH groups on the polymer terminals results in the lowering of the heat-resistance of the aromatic polycarbonate resin.
According to the process of the present invention relating to a catalyst deactivation agent and producing an aromatic polycarbonate resin, an aromatic polycarbonate resin having excellent polymer color can be produced in high efficiency without causing the lowering of molecular weight during the retention at a high temperature up to the discharge of the resin from the polymerization reactor by deactivating the catalyst as quickly as possible after the completion of the polymerization reaction.
In the process of the present invention relating to a catalyst deactivation agent and producing an aromatic polycarbonate resin, the addition timing of the catalyst deactivation agent to be added to the system to eliminate the activity of the catalyst remaining in the aromatic polycarbonate resin at the end of the melt polymerization reaction is preferably within 2 hours, more preferably within 1 hour, further preferably within 30 minutes and most preferably within 15 minutes from the end of the melt polycondensation reaction.
The term xe2x80x9cend of melt polymerization reactionxe2x80x9d means the time when the viscosity-average molecular weight of the produced aromatic polycarbonate resin reaches a target level and the resin is discharged from the evacuated reactor to a non-evacuated state. For example, in the case of using a pump for the discharge of the polymer, the term xe2x80x9cthe addition timing of the catalyst deactivation agent is within 2 hours after the end of the melt polycondensation reactionxe2x80x9d means that the average retention time of the resin in the apparatus from the polymer pump to the addition of the deactivation agent is within 2 hours.
Conventional compounds are effectively usable as the catalyst deactivation agent to be used in the present invention relating to a catalyst deactivation agent and, among these compounds, ammonium salts and phosphonium salts of sulfonic acids are preferable and the above salts of dodecylbenzenesulfonic acid such as dodecylbenzenesulfonic acid tetrabutylphosphonium salt and the above salts of p-toluenesulfonic acid such as p-toluenesulfonic acid tetrabutylammonium salt are more preferable. Other preferably usable compounds are esters of sulfonic acids such as methyl benzenesulfonate, ethyl benzenesulfonate, butyl benzenesulfonate, octyl benzenesulfonate, phenyl benzenesulfonate, methyl p-toluenesulfonate, ethyl p-toluenesulfonate, butyl p-toluenesulfonate, octyl p-toluenesulfonate and phenyl p-toluenesulfonate. Dodecylbenzenesulfonic acid tetrabutyl-phosphonium salt is most preferable among the above compounds.
The addition amount of the catalyst deactivation agent is 0.5 to 50 equivalent, preferably 0.5 to 10 equivalent, more preferably 0.8 to 5 equivalent based on 1 mol of the above main polycondensation catalyst selected from alkali metal compounds and alkaline earth metal compounds. The equivalent of the catalyst deactivation agent is the number of sites reactive with one valence of the catalytic metal and existing in one molecule of the deactivation agent. One mol of the catalyst deactivation agent is equal to one equivalent when the number of said reactive sites is one in one molecule of the deactivation agent or one mol is equal to two equivalent when two reactive sites are present in one molecule. The above addition amount of the catalyst deactivation agent usually corresponds to the use of 0.01 to 500 ppm of the agent based on the aromatic polycarbonate resin.
These catalyst deactivation agents are added and kneaded to a molten aromatic polycarbonate resin directly or in a form dissolved or dispersed in a proper solvent or as a master pellet. There is no particular restriction on the kind of facility to perform the above operation, however, the use of a twin-screw extruder, etc., is preferable. A vent-type twin-screw extruder is especially preferable in the case of using the catalyst deactivation agent in a form dissolved or dispersed in a solvent.
As a result of investigation performed by the inventors of the present invention, it has been found that the foreign matters in an aromatic polycarbonate resin can be removed in extremely high efficiency by a specific filtration treatment.
The aromatic polycarbonate resin in the present invention relating to filtration treatment has no particular restriction. It includes an aromatic polycarbonate resin produced by reacting an aromatic diol compound with a carbonate precursor, such as an aromatic polycarbonate resin produced by interfacial polymerization comprising the reaction of an aromatic diol alkali metal salt with phosgene or an aromatic polycarbonate resin produced by melt polymerization comprising the reaction of an aromatic diol with an aromatic carbonic acid ester. Among these aromatic polycarbonate resins, an aromatic polycarbonate resin produced by melt polymerization method is most suitable for performing the present invention because the resin is directly delivered from a polymerization vessel in molten state, thus eliminating the remelting of the polymer.
There is no particular restriction on the molecular weight of the aromatic polycarbonate resin to be used in the present invention relating to filtration treatment, however, the use of an aromatic polycarbonate resin having a viscosity-average molecular weight of 10,000 or more is preferable as an aromatic polycarbonate resin having a low polymerization degree has an extremely limited application field due to its poor physical properties. Extremely high molecular weight results in the increase of the filtration pressure with a polymer filter, thus a resin having a viscosity-average molecular weight of not higher than 50,000 is suitable for the working of the present invention relating to the filtration treatment.
The filter used in the present invention relating to the filtration treatment is a filter to remove foreign matters existing in an aromatic polycarbonate resin by filtration. Conventional filters such as a candle-type filter, pleats filter and disk-type filter can be used in general and a disk-type filter is most preferable among these filters.
There is no particular restriction on the material of the filter provided that the material is inert to the aromatic polycarbonate resin produced by polymerization and the material is free from components eluted into the aromatic polycarbonate resin. Metals, especially stainless steel are generally used as the material. Preferable material includes SUS304, SUS316, etc.
The term xe2x80x9cretained particle sizexe2x80x9d used in the present invention relating to the filtration treatment means the minimum size (diameter) of particles which can be collected by the filter in a yield of not less than 95% if the shape of the foreign material is spherical. It can also be referred to as xe2x80x9can absolute removal rating.xe2x80x9d
The retained particle size of the polymer filter in the present invention relating to the filtration treatment is 50 xcexcm or less, preferably 40 xcexcm or less, more preferably 20 xcexcm or less, further more preferably 10 xcexcm or less, and especially preferably 5 xcexcm or less. The use of a polymer filter having large retained particle size increases the amount of foreign materials in the produced aromatic polycarbonate resin to an undesirable level.
It seems natural that a polymer containing only a little foreign material can be produced by using a filter having a small retained particle size, however, the decrease of retained particle size increases the dead space and, conversely, often lowers the quality of the obtained polymer.